Old-school brazing (by alaric)

Yesterday, my mate Seth was trying to fix his car exhaust pipe. It had a bit that was made out of corrugated metal tubing, presumably to allow one end of the pipe to vibrate with the engine while the other is fixed.

Anyway, in the way of these things, with all the vibration and heat, it had broken off at one end, leaving the fragmented end of the corrugated thin metal tubing; now without the straight bit of tubing that would nicely clamp around the next bit of pipe.

So we decided to braze it - and due to the scale of the job and the small scale of my supplies of silver solder, to old-school braze it with real brass. After a lot of angle grinder work cleaning the corrugated tube end up and preparing an extension tube made from a tin can (ground down to reveal the steel sheeting within), we smeared a load of flux paste on, heated it up to a orange-ish red, squirted MORE flux paste on, and applied some brass rod I had lying about. To my surprise, it worked - the brass bonded with the existing pipe and the tube we had made from the can. It's a messy job, since the torch couldn't quite keep the heat up enough; the outside of the join is all blobby. If we'd gotten it hotter it would have been a lot runnier and surface tension would have created a smoother surface.

Sealing up the end of the pipe and blowing into the other end produces a slight leak of gas from just one point around the join, too, which was deemed more than good enough.

But with my casting gear still all packed away and the new furnace needing making from scratch anyway, it was great to be messing with hot metal again.

1 Comment

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  By Richard, Sat 10th Oct 2009 @ 3:31 pm

  Ive seen coathangers used to make a solder repair to a car exhaust pipe and it worked great.

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